Google announced support for embedding and using semantic information in gmail messages in either Microdata or JSON-LD. They currently handle several use cases (actions) that use the semantic markup and a way to define new actions.

Providing a way to embed data in JSON-LD should open up the system for experimentation with other vocabularies beyond schema.org. Since the approach just leverages the general ability to embed semantic data in HTML it is not restricted to gmail and can be used by any email environment that supports messages whose content is encoded as HTML.

We hope that this will lead to many exciting ideas, as developers experiment with applications that use the mechanism to embed and understand concepts, entities and facts in email messages.